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  • 28 September 1997 Volume 6 Issue 3
      
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  • Study on quantities of radiation protection in medical X-rays radiation field with polyhedron phantom
    Yuan Shu Yu, et al
    1997, 6(3): 129-132.
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    We have studied tissue-equivalent material with the elemental composition recommended by report No. 44 of ICRU. Three different calibration phantoms in shape have been prepared with the tissue-equivalent material in order to study the influence of the angular dependence factor R (d,α) in the radiation field of X-rays on the calibration of individual dose equivalent Hp (d). The requirement of monogenous radiation field to calibrate several dosimeters on one phantom at the same time can be met by application of dodecahedron phantom, which is difficult on ICRU sphere. Angular dependence factor R (d,α) of 0°~90° and conversion coefficients between individual dose equivalent Hp (0.07,α) and the exposure of radiation of different energies and different angles have been established by taking advantage of the dodecahedron. Besides, we have studied the variation relation between the individual dose equivalent Hp (10,α) and Hp (0.07,α) in the medical X-rays radiation field.
  • Anti-tumor effect of low dose radiation in mice
    Fan Zhengping, et al
    1997, 6(3): 133-135.
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    This paper reports the effects of the total body irradiation of low dose radiation (LDR) and/or the local irradiation of large dose on avarage tumor weights and tumor inhibitory rates in 170 mice inoculated S180 sarcoma cell, and the influence of LDR on avarage longevity in 40 tumor-bearing animals. Results show (1) LDR in the range of 75~250m Gy can inhibit tumor grow th to some extent; (2) fractionated irradiation of 75m Gy and local irradiation of 10Gy may produce a synergism in tumor grow th inhibition; and (3) LDR may enhance avarage longevity in ascitic tumor-bearing mice.
  • Combined effect of 60Coγ-ray and B (a) P on HPRT mutation of human embryo lung cells
    Fan Feiyue, et al
    1997, 6(3): 136-138.
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    HPRT mutation of human embryo lung cells induced by 60Coγ-ray and benzo (a) pyrene was observed in order to study combined effect of radiation and B (a) Pon HPRT mutation of human embryo lung cells. HPRT mutation of the cells occurred after exposed to a different doses of γ-irradiation and B (a) P. Frequencies of HPRT mutations of the cells increased gradually with increase of doses of γ-irradiation and B (a) P. Relationship be tween HPRT mutation and doses of γ-ray or B (a) P was fit into the positive linear corr elation. Variants of HPRT mutation of the cells increased from 0.01±0.02 of control to 0.20±0.02 of 1Gyγ-irradiation and to 0.18±0.03 of lμg/ml B (a) P separately. The variant of the cells exposed to 1Gy γ-ray and lμg/ml B (a) P reached 0.40±0.04, which was not only higher than control's, but also higher than that of γ-ray or B (a) P. The result show ed there was the potentate effect of combined exposure to 60Coγ-irradiation and B (a) P on HPRT mutation of human embryo lung cells.